Using classic Outlook for Windows in business environments
Bad update
In our case there *were* signatures used for different email addresses and selected on a use case basis. Now post change there are multiple mail addresses appearing in the signature box BUT only one signature. The other signatures are their in the background (use ctrl+signatures from the Options|Mail to open the "roaming" folder.
Outlook appears to have arbitrarily chosen one signature on one account (its wrong). All others will now have to be recreated.
This is with IMAP not Outlook/365. So the Outlook team just broke everyone in this use case.